Multi-chip package and method of manufacturing the same

ABSTRACT

A multi-chip package may include a first semiconductor chip, a second semiconductor chip, a first stud bump, a first nail head bonding bump, a second stud bump, and a first conductive wire. The first semiconductor chip may have a first bonding pad. The second semiconductor chip may be stacked on the first semiconductor chip so the first bonding pad remains exposed. The second semiconductor chip may have a second bonding pad. The first stud bump may be formed on the first bonding pad. The first nail head bonding bump may be formed on the first stud bump, with one end of a first conductive wire formed between the two. The second stud bump may be formed on the second bonding pad, with another end of the first conductive wire formed between the two. An electrical connection test may be performed on each of the wire bonding processes.

CROSS-RELATED APPLICATION

This application claims priority under 35 USC §119 to Korean PatentApplication No. 2011-0106379, filed on Oct. 18, 2011 in the KoreanIntellectual Property Office (KIPO), the contents of which are hereinincorporated by reference in their entirety.

BACKGROUND

Example embodiments relate to a multi-chip package and a method ofmanufacturing the same. More particularly, example embodiments relate toa multi-chip package including a plurality of semiconductor chipssequentially stacked, and a method of manufacturing the multi-chippackage.

SUMMARY

Example embodiments provide a multi-chip package having improvedelectrical connection reliability between conductive wires, an improvedstructure on which an electrical connection test of the conductive wiresmay be performed, and a small size.

In one embodiment, a multi-chip package comprises a package substratehaving one or more substrate pads, at least one substrate pad being aground pad and at least one substrate pad being a signal pad; a firstsemiconductor chip having at least a first conductive pad; a secondsemiconductor chip stacked on an upper surface of the firstsemiconductor chip such that the first conductive pad remains exposed,the second semiconductor chip having at least a second conductive pad; afirst stud bump formed on an upper surface of the first conductive pad;a first conductive wire including a first end physically attached to oneof the substrate pads and a second end physically attached to an uppersurface of the first stud bump; a first nail head bonding bump formed onthe first stud bump and the first conductive wire; a second stud bumpformed on an upper surface of the second conductive pad; and a secondconductive wire including a first end physically attached to the firstnail bonding bump and a second end physically attached to an uppersurface of the second stud bump.

In one embodiment, a method of manufacturing a multi-chip packagecomprises providing a package substrate including a plurality ofsubstrate pads disposed on an upper surface of the package substrate,the substrate pads including at least a ground pad and at least a signalpad; stacking a first semiconductor chip on the package substrate, thefirst semiconductor chip including at least a first bonding pad disposedon an upper surface of the first semiconductor chip; stacking at least asecond semiconductor chip on the first semiconductor chip such that thefirst bonding pad remains exposed, the second semiconductor chipincluding at least a second bonding pad disposed on an upper surface ofthe second semiconductor chip; forming a first stud bump on an uppersurface of the first bonding pad; forming a first conductive wire toextend from the substrate pad to an upper surface of the first studbump; forming a first nail head bonding bump on the first stud bump andfirst conductive wire; and after the first semiconductor chip has beenelectrically connected to a ground: forming a second stud bump on anupper surface of the second bonding pad; and forming a second conductivewire extending from an upper surface of the first nail head bonding bumpto the second stud bump.

In one embodiment, a method of manufacturing a multi-chip packagecomprises providing a package substrate including a plurality ofsubstrate pads disposed on an upper surface of the package substrate,the substrate pads including at least a ground pad and at least a signalpad; stacking a first semiconductor chip on the package substrate, thefirst semiconductor chip including at least a first bonding pad disposedon an upper surface of the first semiconductor chip; stacking at least asecond semiconductor chip on the first semiconductor chip such that thefirst bonding pad remains exposed, the second semiconductor chipincluding at least a second bonding pad disposed on an upper surface ofthe second semiconductor chip; forming a first electrical connectionbetween the first semiconductor chip and a ground pad on the packagesubstrate, an end of the electrical connection being formed on a firstconductive bump of the first semiconductor chip; after electricallyconnecting the first semiconductor chip to a ground pad, forming asecond electrical connection from the first semiconductor chip to thesecond semiconductor chip, wherein the step of forming a secondelectrical connection from the first semiconductor chip to the secondsemiconductor chip comprises the steps of: forming a second conductivebump on the end of the first electrical connection disposed on the firstconductive bump of the first semiconductor chip; forming a firstconductive bump on the second semiconductor chip; and forming a firstconductive wire extending from the second conductive bump of the firstsemiconductor chip to the first conductive bump on the secondsemiconductor chip.

BRIEF DESCRIPTION OF THE DRAWINGS

The above and other aspects and features of the disclosure will becomeapparent by describing in detail exemplary embodiments thereof withreference to the attached drawings, in which:

FIG. 1 is a cross-sectional view illustrating a multi-chip package inaccordance with example embodiments;

FIG. 2 is an exemplary plan view illustrating the multi-chip package inFIG. 1;

FIG. 3 is an exemplary perspective view illustrating a packagesubstrate, a first semiconductor chip and a second semiconductor chip ofthe multi-chip package in FIG. 1;

FIGS. 4 to 8 are cross-sectional views illustrating an exemplary methodof manufacturing the multi-chip package in FIG. 1;

FIG. 9 is a cross-sectional view illustrating a multi-chip package inaccordance with example embodiments; and

FIGS. 10 to 15 are cross-sectional views illustrating an exemplarymethod of manufacturing the multi-chip package in FIG. 9.

DETAILED DESCRIPTION OF THE EMBODIMENTS

Various example embodiments will now be described more fully hereinafterwith reference to the accompanying drawings, in which exemplaryembodiments are shown. The present invention may, however, be embodiedin many different forms and should not be construed as limited to theexample embodiments set forth herein. That is, these example embodimentsare just that—examples—and many implementations and variations arepossible that do not require the various details herein. It should alsobe emphasized that the disclosure provides details of alternativeexamples, but such listing of alternatives is not exhaustive.Furthermore, any consistency of detail between various examples shouldnot be interpreted as requiring such detail—it is impracticable to listevery possible variation for every feature described herein. Thelanguage of the claims should be referenced in determining therequirements of the invention. In the drawings, the sizes and relativesize of layers and regions may be exaggerated for clarity. Like numeralsrefer to like elements throughout.

The terminology used herein is for the purpose of describing particularembodiments only and is not intended to limit the invention. As usedherein, the singular terms “a,” “an” and “the” should not exclude theplural forms as well, unless the context clearly indicates otherwise. Asused herein, the term “and/or” includes any and all combinations of oneor more of the associated listed items. It will be understood that whenan element or a layer is referred to as being “on,” “connected to” or“coupled to” another element or layer, it may be directly on, connectedto, or coupled to the other element or layer or intervening elements orlayers may be present. In contrast, when an element is referred to asbeing “directly on,” “directly connected to” or “directly coupled to”another element or layer, there are no intervening elements or layerspresent. Other words used to describe the relationship between elementsor layers should be interpreted in a like fashion (e.g., “between”versus “directly between;” “adjacent” versus “directly adjacent,” etc.).

It will be also understood that although the terms first, second, thirdetc. may be used herein to describe various elements, components,regions, layers and/or sections, these elements, components, regions,layers, and/or sections should not be limited by these terms. Unlessotherwise indicated, these terms are only used to distinguish oneelement, component, region, layer, or section from another element,components, region, layer, or section. Thus, a first element,components, region, layer, or section in some embodiments could betermed a second element, components, region, layer, or section in otherembodiments, and, similarly, a second element, components, region,layer, or section could be termed a first element, components, region,layer, or section without departing from the teachings of thedisclosure. Exemplary embodiments explained and illustrated herein mayinclude their complementary counterparts.

Locational terms, such as “beneath,” “below,” “lower,” “above,” “upper”and the like, may be used herein for ease of description to describe oneelement or feature's relationship to another element(s) or feature(s) asillustrated in the figures. It will be understood that the locationalterms may be relative to a device and are intended to encompassdifferent orientations of the device in use or operation in addition tothe orientation depicted in the figures. For example, if the device inthe figures is turned over, elements described as “below” or “beneath”other elements or features would then be oriented “above” the otherelements or features. Thus, the exemplary term “below” can encompassboth an orientation of above and below. The device may be otherwiseoriented (rotated 90 degrees or at other orientations) and thelocational descriptors used herein interpreted accordingly.

It will be further understood that the terms “comprises”, “comprising,”“includes” and/or “including”, when used herein, specify the presence ofstated features, integers, steps, operations, elements, and/orcomponents, but do not preclude the presence or addition of one or moreother features, integers, steps, operations, elements, components,and/or groups thereof.

Example embodiments are described herein with reference tocross-sectional illustrations that are schematic illustrations ofidealized example embodiments (and intermediate structures) of exampleembodiments. As such, variations from the shapes of the illustrations asa result, for example, of manufacturing techniques and/or tolerances,are to be expected. Example embodiments should not be construed aslimited to those shown in the views, but include modifications inconfiguration formed on the basis of, for example, manufacturingprocesses. For example, an implanted region illustrated as a rectanglemay have rounded or curved features and/or a gradient of implantconcentration at its edges rather than a binary change from implanted tonon-implanted region. Likewise, a buried region formed by implantationmay result in some implantation in the region between the buried regionand the surface through which the implantation takes place. Thus, theregions illustrated in the figures may be schematic in nature and theirshapes are not intended to limit the scope of the present disclosure.

Terms such as “same,” “planar,” or “coplanar,” as used herein whenreferring to orientation, layout, location, shapes, sizes, amounts, orother measures do not necessarily mean an exactly identical orientation,layout, location, shape, size, amount, or other measure, but areintended to encompass nearly identical orientation, layout, location,shapes, sizes, amounts, or other measures within acceptable variationsthat may occur, for example, due to manufacturing processes.

Unless otherwise defined, all terms (including technical and scientificterms) used herein have the same meaning as commonly understood by oneof ordinary skill in the art to which this disclosure belongs. It willbe further understood that terms, such as those defined in commonly useddictionaries, should be interpreted as having a meaning that isconsistent with their meaning in the context of the relevant art and/orthe present application and will not be interpreted in an idealized oroverly formal sense unless expressly so defined herein.

Hereinafter, example embodiments will be explained in detail withreference to the accompanying drawings.

Generally, a plurality of semiconductor fabrication processes may beperformed on a semiconductor substrate to form a plurality ofsemiconductor chips. In order to mount the semiconductor chips on aprinted circuit board (PCB), a packaging process may be performed onsemiconductor chips to form semiconductor packages.

In order to increase a storage capacity of the semiconductor package, amulti-chip package including a plurality of the semiconductor chipssequentially stacked may be widely developed. The stacked semiconductorchips may be electrically connected with each other via conductivewires.

The semiconductor chips of the multi-chip package may have astair-stepped structure. Each of the stair-stepped semiconductor chipsmay have an exposed upper edge portion. Bonding pads may be arranged onthe exposed upper edge portion of each of the stair-steppedsemiconductor chips. The bonding pads may be electrically connected witheach other via the conductive wires. The conductive wires may beconnected to the bonding pads via conductive bumps such as a stud bumpand/or a nail head bonding bump.

When the conductive wire is connected to the bonding pad via only thenail head bonding bump, a conductive wire with a very thin thickness maybe directly connected to the nail head bonding bump. This may require avery high accuracy of a wire bonding process. A thin conductive wire maynot be accurately or reliably connected to the nail head bonding bump.

When the conductive wire is connected to the bonding pad via the studbump and the nail head bump, a nail head bonding bump having a largesize may be placed on the stud bump having a large size, such thatelectrical connection reliability between the conductive wire and thebonding pad may be improved. In this scenario, however, according torelated wire bonding methods, the conductive wire may extend from abonding pad of an upper semiconductor chip to a bonding pad of a lowersemiconductor chip. A process for electrically connecting a bonding padof a lowermost semiconductor chip with a ground pad of a packagesubstrate may be performed as one of the last steps of the multi-chippackage fabrication. In this case, although an abnormal conductive wiremay be generated, the abnormal conductive wire may not be detectedbefore grounding the bonding pad of the lowermost semiconductor chip.With the conventional wire bonding methods for multi-chip packages,before the grounding process, it may not be possible to test electricalconnections between the conductive wires.

In the conventional method, the conductive wire may possibly makecontact with an edge portion of the semiconductor chip. In order toprevent the contact between the conductive wire and the edge portion ofthe semiconductor chip, it may be required to enlarge an area of theexposed upper edge portion of the lower semiconductor chip. As a result,the multi-chip package may have a wide width.

FIG. 1 is a cross-sectional view illustrating a multi-chip package inaccordance with example embodiments, FIG. 2 is a plan view illustratingthe exemplary multi-chip package in FIG. 1, and FIG. 3 is a perspectiveview illustrating a package substrate, a first semiconductor chip and asecond semiconductor chip of the exemplary multi-chip package in FIG. 1.

Referring to FIGS. 1 to 3, a multi-chip package 100 of this exampleembodiment may include a package substrate 110, a first semiconductorchip 120, a second semiconductor chip 130, a first stud bump 124, afirst nail head bonding bump 126, a second stud bump 134, a substratewire 150, a first conductive wire 152, a molding member 140 and externalterminals 128.

The package substrate 110 may have substrate pads 112. In exampleembodiments, the substrate pads 112 may be arranged at an upper surfaceof the package substrate 110. In some embodiments, some or all of thesubstrate pads 112 are arranged on an edge of the upper surface of thepackage substrate 110. The substrate pads 112 may include at least onesignal pad and at least one ground pad. The substrate pads 112 may beany conductive pad or terminal disposed on the upper surface of thepackage substrate 110, through which signals and/or power may betransmitted.

The first semiconductor chip 120 may be disposed on an upper surface ofthe package substrate 110. In example embodiments, the firstsemiconductor chip 120 may be attached to the upper surface of thepackage substrate 110 using an adhesive 114. The first semiconductorchip 120 may be positioned on the upper surface of the package substrate110 such that the substrate pads 112 remain exposed. The firstsemiconductor chip 120 may include a plurality of first bonding pads122. The first bonding pads 122 may be disposed on an edge portion of anupper surface of the first semiconductor chip 120. The first bondingpads 122 may be any conductive pad or terminal disposed on the uppersurface of the first semiconductor chip 120 through which signals and/orpower may be transmitted.

The second semiconductor chip 130 may be disposed on the upper surfaceof the first semiconductor chip 120. In example embodiments, the secondsemiconductor chip 130 may be attached to the upper surface of the firstsemiconductor chip 120 using the adhesive 114. The second semiconductorchip 130 may be positioned on the upper surface of the firstsemiconductor chip 120 such that the first bonding pads 122 remainexposed. The package substrate 110, the first semiconductor chip 120 andthe second semiconductor chip 130 may have a stepped or stair structure.The second semiconductor chip 130 may include a plurality of secondbonding pads 132. The second bonding pads 132 may be disposed on an edgeportion of an upper surface of the second semiconductor chip 130. Thesecond bonding pads 132 may be any conductive pad or terminal disposedon the upper surface of the second semiconductor chip 130 through whichsignals and/or power may be transmitted.

The first stud bumps 124 may be formed on the first bonding pads 122. Inexample embodiments, the first stud bump 124 may be formed by applying aspark to an end of a metal line (not shown) drawn from a capillary (notshown) that may be used for forming the substrate wire 150 and the firstconductive wire 152. In some embodiments, the first stud bump 124, thesubstrate wire 150 and the first conductive wire 152 may include thesame material. The first stud bumps 124 may be conductive connectorsformed in the manner described above, and through which signals and/orpower may be transmitted. For example, the first stud bumps 124 may beconductive bumps, conductive balls, etc.

The substrate wire 150 may be a conductive connector that electricallyconnects the substrate pad 112 and the first stud bump 124. For example,the substrate wire 150 may be extended from the substrate pad 112 to anupper end of the first stud bump 124. The first semiconductor chip 120and the package substrate 110 may be electrically connected with eachother, such that signals may be passed and/or logical communication mayoccur between the two, via the first stud bump 124 and the substratewire 150. The substrate wire 150 may be physically connected to a topsurface of the first stud bump 124. The substrate wire 150 may be, forexample, welded to the top surface of the first stud bump 124. In otherembodiments, heat may be applied to the metal line (not shown) fromwhich the substrate wire is formed, at a point where the metal linecontacts a top surface of the first stud bump 124, thereby forming aphysical connection between the substrate wire 150 and the first studbump 124. In some embodiments, the surface area of the first stud bump124 that is in contact with the first bonding pad 122 may be at leasthalf as large as the surface area of the upper surface of the firstbonding pad 122. In some embodiments, the surface area of the first studbump 124 in contact with the first bonding pad 122 may be the same sizeas the surface area of the upper surface of the first bonding pad 122.

In example embodiments, the substrate wire 150 may also be electricallyconnected to the ground pad of the substrate pads 112. Correspondingly,the first semiconductor chip 120 may be connected to the ground pad. Inthese embodiments, it may be possible to perform an electricalconnection test between the first semiconductor chip 120 and the packagesubstrate 110.

The first nail head bonding bump 126 may be formed on the first studbump 124. As mentioned above, the substrate wire 150 may be disposed ona top surface of the first stud bump 124, such that the substrate wire150 may be interposed between the first stud bump 124 and the first nailhead bonding bump 126. In example embodiments, the first nail headbonding bump 126 may be formed by applying a spark to an end of themetal line (not shown) drawn from the capillary (not shown). The firstnail head bonding bump 126 may include a material the same as that ofthe first stud bump 124, the substrate wire 150 and the first conductivewire 152. The first nail head bonding bump 126 may be a conductiveconnector formed in the manner described above, and through whichsignals and/or power may be transmitted. For example, the first nailhead bonding bump 126 may be conductive bumps, conductive balls, etc.

In some embodiments, the surface area of a lower surface of the firstnail head bonding bump 126 that faces an upper surface of the first studbump 124 may be twice as large as the surface area of the upper surfaceof the first stud bump 124. In some embodiments, the surface area of alower surface of the first nail head bonding bump 126 that faces anupper surface of first stud bump 124 may be the same size as the surfacearea of the upper surface of the first stud bump 124.

In example embodiments, the electrical connection between the firstsemiconductor chip 120 and the second semiconductor chip 130 may beenhanced due to increased contact between the first nail head bondingbump 126 and the first stud bump 124. The first nail head bonding bump126 and the first stud bump 126 may have cross-sectional areasoverlapping each other larger than those of the substrate wire 150 andthe first conductive wire 152. The electrical connection between thefirst semiconductor chip 120 and the second semiconductor chip 130 mayhave improved reliability with the use of the nail head bonding bump 126and the first stud bump 126 in the example configurations.

The second stud bump 134 may be formed on the second bonding pad 132. Inexample embodiments, the second stud bump 134 may be formed by applyinga spark to an end of the metal line drawn from the capillary. The secondstud bump 134 may be similar to the first stud bump 124. For example,the second stud bump 134 may be of one of the same types as the firststud bump 124 and may be made of similar or the same material.

The first conductive wire 152 may a conductive wire that mayelectrically connects the first nail head bonding bump 126 and thesecond stud bump 134. In some embodiments, the first conductive wire 152may extend from the upper end of the first nail head bonding bump 126 toan upper end of the second stud bump 134. Correspondingly, the secondsemiconductor chip 130 may be connected with the ground pad via thefirst conductive wire 152 and the substrate wire 150. In theseembodiments, it may be possible to perform an electrical connection testbetween the first semiconductor chip 120 and the second semiconductorchip 130. The first conductive wire 152 may be similar to the substratewire 150. For example, the first conductive wire 152 may be made of thesame or similar material as the substrate wire 150.

In example embodiments, the first conductive wire 152 may be connectedto the upper end of the first nail head bonding bump 126, and not to aside surface of the first nail head bonding bump 126. In these examples,the likelihood of contact between the first conductive wire 152 and anupper end of a side surface of the second semiconductor chip 130 isminimal and may be prevented. The end of the first conductive wire 152connected to the first nail head bonding bump 126 is elevated ascompared to being connected merely to a pad or terminal on the firstsemiconductor chip 120. Given the increased elevation of the end of thefirst conductive wire 152 connected to the first semiconductor chip, thespace between the first nail head bonding bump 126 and a verticalsurface of the second semiconductor chip 130 contacting the firstsemiconductor chip 120 may be reduced. In some embodiments, the width ofspace between the first bonding pad 122 of the first semiconductor chip120 and the vertical side surface of the second semiconductor chip 130may be the same as a half of a width of the capillary. Because the firstconductive wire 152 is physically connected to a top of the first nailhead bonding bump 126 and not to a side surface thereof, the amount ofthe space between the first bonding pad 122 and a vertical side surfaceof the second semiconductor chip 130 may be set regardless of the widthof the first conductive wire 152. In these embodiments, a portion of thefirst semiconductor chip 120 extending past the second semiconductorchip 130 in a step or stair fashion may have a narrow width.Correspondingly, the multi-chip package 100 may also have a narrowwidth.

The molding member 140 may be formed on the upper surface of the packagesubstrate 110 to cover the first semiconductor chip 120, the secondsemiconductor chip 130, the substrate wire 150 and the first conductivewire 152. The molding member 140 may protect the first semiconductorchip 120, the second semiconductor chip 130, the substrate wire 150 andthe first conductive wire 152 from external environments. In exampleembodiments, the molding member 140 may include an epoxy moldingcompound (EMC) or may be any other suitable material (e.g. anyinsulative, non-conductive material).

The external terminals 128 may be mounted on a lower surface of thepackage substrate 110. The external terminals 128 may be electricallyconnected to the substrate pads 112. In example embodiments, theexternal terminals 128 may include conductive connectors such as solderballs, conductive plugs, conductive leads, and so forth.

FIGS. 4 to 8 are cross-sectional views illustrating an exemplary methodof manufacturing the multi-chip package in FIG. 1.

Referring to FIG. 4, the first semiconductor chip 120 may be attached tothe upper surface of the package substrate 110 using the adhesive 114.The first semiconductor chip 120 may be disposed on the upper surface ofthe package substrate 110 such that the substrate pad 112 of the packagesubstrate 110 may remain exposed and not covered or rendered unusable bythe first semiconductor chip 120.

The second semiconductor chip 130 may be attached to the upper surfaceof the first semiconductor chip 120 using the adhesive 114. The secondsemiconductor chip 130 may be disposed on the upper surface of the firstsemiconductor chip 120 such that the first bonding pad 122 of the firstsemiconductor chip 120 remains exposed and not covered or renderedunusable by the second semiconductor chip 130.

The capillary 180 may be positioned over the first bonding pad 122. Ametal line 190 may be drawn through a hole of the capillary 180. Forexample, the capillary 180 may be a needle-like tool through which ametal line 190 is drawn. The metal line 190 may extend past a first endof the capillary 180 and may be contained in a spool like structure pastthat first end of the capillary 180. A small length of the metal line190 may extend past the other end (the second end) of the capillary 180and may be used to form structures or enable the forming of structuresof the multi-chip package 100. A spark may be applied to the end of themetal line 190 extending past the capillary 180 to form the first studbump 124. In some embodiments, a spark may be a high voltage electriccharge that is applied to the metal line 190 that melts the metal line190 at the tip of the capillary 180 to form the first stud bump 124. Thefirst stud bump 124 may be shaped like a ball due to the surface tensionof the molten metal of the metal line 190.

The first stud bump 124 may be disposed on a top surface of the firstbonding pad 122. A supersonic wave may be applied to the first stud bump124 to bond the first stud bump 124 to the first bonding pad 122. Forexample, the capillary 180 may be lowered to be positioned at a topsurface of the first stud bump 124. The first semiconductor chip 120 maybe heated to at least 125 degrees Celsius. The capillary 180 may applyultra sonic energy, such as a supersonic wave, to the first stud bump124. The combined heat, pressure, and supersonic energy may create aweld between the first stud bump 124 and the first bonding pad 122.After the first stud bump 124 has been bonded to the first bonding pad122, the metal line 190 may then be cut to separate the first stud bump124 from the metal line 190.

Referring to FIG. 5, the capillary 180 may be positioned at a top of thesubstrate pad 112. A first end of the metal line 190 may be bonded tothe substrate pad 112. For example, heat or a spark may be applied tomelt a small portion of the metal line 190 to the substrate pad 112. Thecapillary 180 may then be positioned at a top of the first stud bump124, with one end of the metal line physically connected to thesubstrate pad 112 such that a length of metal line from the substratepad 112 to the top of the first stud bump 124 extends past one end ofthe capillary 190. The metal line 190 may be physically connected at theupper end of the first stud bump 124, such that a portion of the metalline 190 physically connects the substrate pad 112 and the first studbump 124. For example, a spark may be applied to the metal line 190 atthe upper surface of the first stud bump 124 to physically connect themetal line 190 to the first stud bump 124, thereby forming the substratewire 150 between the substrate pad 112 and the first stud bump 124. Themetal line 190 may then be separated from the substrate wire 150.

As mentioned above, in example embodiments, the substrate pad 112 mayinclude one or more signal pads and one or more ground pads.Correspondingly, the first semiconductor chip 120 may be connected withthe ground pad through the substrate wire 150. In these embodiments, itmay be possible to perform the electrical connection test between thefirst semiconductor chip 120 and the package substrate 110.

Referring to FIG. 6, a spark may be applied to a lower end of the metalline 190 to form the first nail head bonding bump 126. The capillary 180may then be descended toward the first stud bump 124 to bond the firstnail head bonding bump 126 to the first stud bump 124. The metal line190 may then be separated from the first nail head bonding bump 126. Thefirst nail head bonding bump 126 may be formed in a manner similar tothe forming of the first stud bump 124. The first nail head bonding bump126 may be bonded to the first stud bump 124 in a manner similar to thebonding of the first stud bump 124 to the first bonding pad 122.

Referring to FIG. 7, a spark may be applied to a lower end of the metalline 190 to form the second stud bump 134. The second stud bump 134 maybe disposed on the second bonding pad 132. A supersonic wave may beapplied to the second stud bump 134 to bond the second stud bump 134 tothe second bonding pad 132. The metal line 190 may then be separatedfrom the second stud bump 134. The second stud bump 134 may be formed ina manner similar to the forming of the first stud bump 124. The secondstud bump 134 may be bonded to the second bonding pad 132 in a mannersimilar to the bonding of the first stud bump 124 to the first bondingpad 122.

Referring to FIG. 8, the metal line 190 may be extended, via thecapillary 180, from the first nail head bonding bump 126 to the secondstud bump 134 to form the first conductive wire 152 between first nailhead bonding bump 126 and the second stud bump 134. The metal line 190may then be separated from the first conductive wire 152. The firstconductive wire 152 may be formed and connected to the first nail headbonding bump 126 and the second stud bump 134 in a manner similar to theforming and connection of the substrate wire 150.

In example embodiments, the second semiconductor chip 130 may beconnected with the ground pad via the first conductive wire 152 and thesubstrate wire 150. In these embodiments, it may be possible to performthe electrical connection test between the first semiconductor chip 120and the second semiconductor chip 130.

As mentioned above, in example embodiments, the first conductive wire152 may be connected to the upper end of the first nail head bondingbump 126, not to a side surface of the first nail head bonding bump 126.In these examples, the likelihood of contact between the firstconductive wire 152 and an upper end of a side surface of the secondsemiconductor chip 130 is minimal and may be prevented. Also, the spacebetween the first nail head bonding bump 126 and an vertical surface ofthe second semiconductor chip 130 contacting the first semiconductorchip 120 may be reduced. In some embodiments, the width of space betweenthe first bonding pad 122 of the first semiconductor chip 120 and thevertical side surface of the second semiconductor chip 130 may be thesame as a half of a width of the capillary. As mentioned above, theamount of the space between the first bonding pad 122 and a verticalside surface of the second semiconductor chip 130 may be set regardlessof the width of the first conductive wire 152. In these embodiments, aportion of the first semiconductor chip 120 extending past the secondsemiconductor chip 130 in a step or stair fashion may have a narrowwidth. Correspondingly, the multi-chip package 100 may also have anarrow width.

The molding member 140 may be formed on the upper surface of the packagesubstrate 110 to cover the first semiconductor chip 120, the secondsemiconductor chip 130, the substrate wire 150 and the first conductivewire 152.

The external terminals 128 may be mounted on the lower surface of thepackage substrate 110 to complete the multi-chip package 100 in FIG. 1.

FIG. 9 is a cross-sectional view illustrating a multi-chip package inaccordance with example embodiments.

A multi-chip package 100 a of this example embodiment may includeelements similar to or the same as those of the multi-chip package 100in FIG. 1 except for further including a third semiconductor chip 160, afourth semiconductor chip 170, a second conductive wire 154 and a thirdconductive wire 156. Thus, the same reference numerals may refer to thesame elements and any further illustrations with respect to the sameelements may be omitted herein for brevity.

Referring to FIG. 9, the third semiconductor chip 160 may be attached tothe upper surface of the second semiconductor chip 130 using theadhesive 114. The third semiconductor chip 160 may be disposed on theupper surface of the second semiconductor chip 130 such that the secondbonding pad 122 of the second semiconductor chip 130 may remain exposedand not covered or rendered unusable by the third semiconductor chip160.

The fourth semiconductor chip 170 may be attached to the upper surfaceof the third semiconductor chip 160 using the adhesive 114. The fourthsemiconductor chip 170 may be disposed on the upper surface of the thirdsemiconductor chip 160 such that the third bonding pad 132 of the thirdsemiconductor chip 160 remains exposed and not covered or renderedunusable by the fourth semiconductor chip 170.

A second nail head bonding bump 136 may be formed on the second studbump 134. One end of the first conductive wire 152 may be disposed on atop surface of the second stud bump 134, such that the first conductivewire 152 may be interposed between the second stud bump 134 and thesecond nail head bonding bump 136. The second nail head bonding bump 136may be similar to the first nail head bonding bump 126. For example, thesecond nail head bonding bump 136 may be formed in a manner similar tothe forming of the first nail head bonding bump 126 or may be of thesame or similar materials as the first nail head bonding bump 126.

A third stud bump 164 may be formed on the third bonding pads 162. Thethird stud bump 164 may be similar to the second stud bump 134. Forexample, the third stud bump 164 may be formed in a manner similar tothe forming of the second stud bump 134 or may be of the same or similarmaterials as the second stud bump 134. A second conductive wire 154 mayelectrically connect between the second nail head bonding bump 136 andthe third stud bump 164, such that signals and logical communicationsmay be transmitted via the second conductive wire 154 to the second nailhead bonding bump 136 and the third stud bump 164. The second conductivewire 154 may be similar to the first conductive wire 152. For example,the second conductive wire 154 may be formed in a manner similar to theforming of the first conductive wire 152 or may be of the same orsimilar materials as the first conductive wire 152.

A third nail head bonding bump 166 may be formed on the third stud bump164. One end of the second conductive wire 154 may be disposed on a topsurface of the third stud bump 164, such that the second conductive wire154 may be interposed between the third stud bump 164 and the third nailhead bonding bump 166. The third nail head bonding bump 166 may besimilar to the second nail head bonding bump 136. For example, the thirdnail head bonding bump 166 may be formed in a manner similar to theforming of the second nail head bonding bump 136 or may be of the sameor similar materials as the second nail head bonding bump 136.

A fourth stud bump 174 may be formed on the fourth bonding pad 172. Thefourth stud bump 174 may be similar to the third stud bump 164. Forexample, the fourth stud bump 174 may be formed in a manner similar tothe forming of the third stud bump 164 or may be of the same or similarmaterials as the third stud bump 164. A third conductive wire 156 mayelectrically connect between the third nail head bonding bump 166 andthe fourth stud bump 174, such that signals and logical communicationsmay be transmitted via the third conductive wire 156 to the third nailhead bonding bump 166 and the fourth stud bump 174. The third conductivewire 156 may be similar to the second conductive wire 1524. For example,the third conductive wire 156 may be formed in a manner similar to theforming of the second conductive wire 154 or may be of the same orsimilar materials as the second conductive wire 154.

FIGS. 10 to 15 are cross-sectional views illustrating a method ofmanufacturing the multi-chip package in FIG. 9.

Processes similar or the same as those illustrated with reference toFIGS. 4 to 8 may be performed to electrically connect the firstsemiconductor chip 120 and the second semiconductor chip 130 using thefirst conductive wire 152.

Referring to FIG. 10, the third semiconductor chip 160 may be attachedto the upper surface of the second semiconductor chip 130 using theadhesive 114. The third semiconductor chip 160 may be disposed on theupper surface of the second semiconductor chip 130 such that the secondbonding pad 122 of the second semiconductor chip 130 may remain exposedand not covered or rendered unusable by the third semiconductor chip160.

The fourth semiconductor chip 170 may be attached to the upper surfaceof the third semiconductor chip 160 using the adhesive 114. The fourthsemiconductor chip 170 may be disposed on the upper surface of the thirdsemiconductor chip 160 such that the third bonding pad 132 of the thirdsemiconductor chip 160 may remain exposed and not covered or renderedunusable by the fourth semiconductor chip 170.

A spark may be applied to a lower end of the metal line 190 to form thesecond nail head bonding bump 136. The second nail head bonding bump 136may be bonded to the second stud bump 134. The metal line 190 may thenbe separated from the second nail head bonding bump 136. The process offorming the second nail head bonding bump 136 may be similar to theprocess of forming the first nail head bonding bump 126. The process ofbonding the second nail head bonding bump 136 to the second stud bump134 may be the same or similar to the process of bonding the first nailhead bonding bump 126 to the first stud bump 124.

Referring to FIG. 11, a spark may be applied to a lower end of the metalline 190 to form the third stud bump 164. The third stud bump 164 may beplaced on the third bonding pad 162. A supersonic wave may be applied tothe third stud bump 164 to bond the third stud bump 164 to the thirdbonding pad 162. The metal line 190 may be cut to separate the metalline 190 from the third stud bump 164. The process of forming the thirdstud bump 164 may be the same or similar to the process of forming thefirst stud bump 124. The process of bonding the third stud bump 164 tothe third bonding pad 162 may be the same or similar to the process ofbonding the first stud bump 124 to the first bonding pad 122.

Referring to FIG. 12, a lower end of the metal line 190 may be extendedfrom the second nail head bonding bump 136 to the third stud bump 164 toform the second conductive wire 154 between the second nail head bondingbump 136 and the third stud bump 164. The metal line 190 may then beseparated from the second conductive wire 154. The process of formingthe second conductive wire 154 may be the same or similar to the processof forming the first conductive wire 152.

Referring to FIG. 13, a spark may be applied to a lower end of the metalline 190 to form the third nail head bonding bump 166. The third nailhead bonding bump 166 may be bonded to the third stud bump 164. Themetal line 190 may then be separated from the third nail head bondingbump 166. The process of forming the third nail head bonding bump 166may be the same or similar to the process of forming the first nail headbonding bump 126. The process of bonding the third nail head bondingbump 166 to the third stud bump 164 maybe the same or similar to theprocess of bonding the first nail head bonding bump 126 to the firststud bump 124.

Referring to FIG. 14, a spark may be applied to a lower end of the metalline 190 to form the fourth stud bump 174. The fourth stud bump 174 maybe placed on the fourth bonding pad 172. A supersonic wave may beapplied to the fourth stud bump 174 to bond the fourth stud bump 174 tothe fourth bonding pad 172. The metal line 190 may then be separatedfrom the second stud bump 174. The process of forming the fourth studbump 764 may be the same or similar to the process of forming the firststud bump 124. The process of bonding the fourth stud bump 174 to thefourth bonding pad 172 may be the same or similar to the process ofbonding the first stud bump 124 to the first bonding pad 122.

Referring to FIG. 15, the metal line 190 may be extended from the thirdnail head bonding bump 166 to the fourth stud bump 174 to form the thirdconductive wire 156 between the third nail head bonding bump 166 and thefourth stud bump 174. The metal line 190 may then be separated from thethird conductive wire 156. The process of forming the third conductivewire 156 may be the same or similar to the process of forming the firstconductive wire 152.

The molding member 140 may be formed on the package substrate 110 tocover the first semiconductor chip 120, the second semiconductor chip130, the third semiconductor chip 160 and the fourth semiconductor chip170.

The external terminals 128 may be mounted on the lower surface of thepackage substrate 110 to complete the multi-chip package 100 a in FIG.9.

In example embodiments, the multi-chip package may include the twosemiconductor chips or the four semiconductor chips. Alternatively, themulti-chip package may further include three semiconductor chips, atleast five semiconductor chips, etc. The multi-chip package describedherein may include a plurality of semiconductor chips stacked in astepped or staired manner at least at one end of the package. One ormore of the semiconductor chips of the multi-chip package may be amemory chip, and one or more of the semiconductor chips may be a logicchip, may act as a processor, etc. The multi-chip package could be partof a device such as personal data assistant (PDA), smart phone, camera,LCD, computer laptop, memory card, etc.

According to example embodiments, after the semiconductor chip isgrounded to the package substrate, the wire bonding processes may beperformed from a lowermost semiconductor chip to an uppermostsemiconductor chip. An electrical connection test between the conductivewires may be performed for each of the wire bonding processes, forexample, after a first chip is connected to a substrate via a wirebonding, but before the first chip is connected to a second chip viawire bonding. In these example embodiments, the nail head bonding bumpmay be formed on the stud bump, so that the conductive wires may haveimproved electrical connection reliability. In these exampleembodiments, the conductive wire may be connected to the upper end ofthe nail head bonding bump, so that the conductive wire may not makecontact with an edge portion of the semiconductor chip. Correspondingly,a narrow gap may be provided between the nail head bonding bump and theedge portion of the semiconductor chip may be narrow, so that themulti-chip package may have a small size.

The above-disclosed subject matter is to be considered illustrative andnot restrictive, and the appended claims are intended to cover all suchmodifications, enhancements, and other embodiments, which fall withinthe true spirit and scope of the disclosed embodiments. Thus, theinvention is to be construed by the broadest permissible interpretationof the following claims and their equivalents, and shall not berestricted or limited by the foregoing detailed description.

What is claimed is:
 1. A multi-chip package comprising: a packagesubstrate having one or more substrate pads, at least one substrate padbeing a ground pad and at least one substrate pad being a signal pad; afirst semiconductor chip having at least a first conductive pad; asecond semiconductor chip stacked on an upper surface of the firstsemiconductor chip such that the first conductive pad remains exposed,the second semiconductor chip having at least a second conductive pad; afirst stud bump formed on an upper surface of the first conductive pad;a first conductive wire including a first end physically attached to oneof the substrate pads and a second end physically attached to an uppersurface of the first stud bump; a first nail head bonding bump formed onthe first stud bump and the first conductive wire; a second stud bumpformed on an upper surface of the second conductive pad; and a secondconductive wire including a first end physically attached to the firstnail bonding bump and a second end physically attached to an uppersurface of the second stud bump.
 2. The multi-chip package of claim 1,further comprising: a second nail head bonding bump formed on the secondstud bump and the second conductive wire.
 3. The multi-chip package ofclaim 1, wherein the first stud bump, first conductive wire, and firstnail head bonding bump are conductors formed from a same metal line. 4.The multi-chip package of claim 1, wherein a surface area of the firststud bump in contact with the first bonding pad is at least 50% the sizeof the surface area of the upper surface of the first bonding pad. 5.The multi-chip package of claim 4, wherein a surface area of a lowersurface of the first nail head bonding bump that faces the upper surfaceof the first stud bump is at least 50% of the size of the surface areaof the upper surface of the first stud bump.
 6. The multi-chip packageof claim 2, further comprising: a third semiconductor chip stacked on anupper surface of the second semiconductor chip such that the secondconductive pad remains exposed, the third semiconductor chip having oneor more third conductive pads; a third stud bump formed on an uppersurface of the third conductive pad; a third conductive wire including afirst end physically attached to one of the second nail head bondingbumps and a second end physically attached to an upper surface of thethird stud bump.
 7. The multi-chip package of claim 1, furthercomprising a molding member formed on an upper surface of the packagesubstrate, the molding member disposed to cover the first semiconductorchip and the second semiconductor chip.
 8. The multi-chip package ofclaim 1, further comprising a plurality of external terminals disposedon a lower surface of the package substrate.
 9. A method ofmanufacturing a multi-chip package, the method comprising: providing apackage substrate including a plurality of substrate pads disposed on anupper surface of the package substrate, the substrate pads including atleast a ground pad and at least a signal pad; stacking a firstsemiconductor chip on the package substrate, the first semiconductorchip including at least a first bonding pad disposed on an upper surfaceof the first semiconductor chip; stacking at least a secondsemiconductor chip on the first semiconductor chip such that the firstbonding pad remains exposed, the second semiconductor chip including atleast a second bonding pad disposed on an upper surface of the secondsemiconductor chip; forming a first stud bump on an upper surface of thefirst bonding pad; forming a first conductive wire to extend from thesubstrate pad to an upper surface of the first stud bump; forming afirst nail head bonding bump on the first stud bump and first conductivewire; and after the first semiconductor chip has been electricallyconnected to a ground: forming a second stud bump on an upper surface ofthe second bonding pad; and forming a second conductive wire extendingfrom an upper surface of the first nail head bonding bump to the secondstud bump.
 10. The method of claim 9, further comprising: after formingthe second conductive wire, forming a second nail head bonding bump onthe second stud bump and second conductive wire.
 11. The method of claim9, wherein the first stud bump, first conductive wire, and first nailhead are formed from a same metal line.
 12. The method of claim 9,wherein a surface area of the first stud bump in contact with the firstbonding pad is at least 50% the size of the surface area of the uppersurface of the first bonding pad.
 13. The method of claim 12, wherein asurface area of a lower surface of the first nail head bonding bump thatfaces the upper surface of the first stud bump is at least 50% of thesize of the surface area of the upper surface of the first stud bump.14. The method of claim 9, further comprising: testing an electricalconnectivity of the first semiconductor chip, wherein the step oftesting is performed after forming the first conductive wire.
 15. Themethod of claim 9, further comprising: testing an electricalconnectivity of the first semiconductor chip, wherein the step oftesting is performed after forming the first conductive wire and beforeforming the second stud bump.
 16. A method of manufacturing a multi-chippackage, comprising: providing a package substrate including a pluralityof substrate pads disposed on an upper surface of the package substrate,the substrate pads including at least a ground pad and at least a signalpad; stacking a first semiconductor chip on the package substrate, thefirst semiconductor chip including at least a first bonding pad disposedon an upper surface of the first semiconductor chip; stacking at least asecond semiconductor chip on the first semiconductor chip such that thefirst bonding pad remains exposed, the second semiconductor chipincluding at least a second bonding pad disposed on an upper surface ofthe second semiconductor chip; forming a first electrical connectionbetween the first semiconductor chip and a ground pad on the packagesubstrate, an end of the electrical connection being formed on a firstconductive bump of the first semiconductor chip; and after electricallyconnecting the first semiconductor chip to a ground pad, forming asecond electrical connection from the first semiconductor chip to thesecond semiconductor chip, wherein the step of forming a secondelectrical connection from the first semiconductor chip to the secondsemiconductor chip comprises the steps of: forming a second conductivebump on the end of the first electrical connection disposed on the firstconductive bump of the first semiconductor chip; forming a firstconductive bump on the second semiconductor chip; and forming a firstconductive wire extending from the second conductive bump of the firstsemiconductor chip to the first conductive bump on the secondsemiconductor chip.
 17. The method of claim 16, wherein: forming thefirst conductive bump on the first semiconductor chip comprises forminga first stud bump on an upper surface of the first bonding pad; formingthe second conductive bump on an end of the of the first electricalconnection comprises forming a first nail head bonding bump on the firststud bump and first electrical connection; forming a first conductivebump on the second semiconductor chip comprises forming a second studbump on an upper surface of the second bonding pad.
 18. The method ofclaim 16, further comprising: stacking a third semiconductor chip on thesecond semiconductor chip such that the second bonding pad remainsexposed, the third semiconductor chip including at least a third bondingpad disposed on an upper surface of the third semiconductor chip;electrically connecting the third semiconductor chip and the secondsemiconductor chip, wherein the step of stacking the third semiconductorchip is performed before the step of electrically connecting the firstsemiconductor chip and the second semiconductor chip, and wherein thestep of electrically connecting the third semiconductor chip and thesecond semiconductor chip is performed after the step of electricallyconnecting the first semiconductor chip and the second semiconductorchip.
 19. The method of claim 17, further comprising: testing anelectrical connectivity of the first semiconductor chip, wherein thestep of testing is performed after forming the first electricalconnection.
 20. The method of claim 16, further comprising: testing anelectrical connectivity of the first semiconductor chip, wherein thestep of testing is performed after forming the first electricalconnection and before forming the first conductive bump on the secondsemiconductor chip.